Electron discharge device



Aug. 18, 1942. H M WAGNER 2,293,418

ELECTRON DISCHARGE DEVICE Filed Sept. 27, 1940 3 Sheets-Sheet l OUTPUT ATTORNE Y A ug. 18, 1942. H'. M. WAGNER 2,293,418

ELECTRON DISCHARGE DEVICE Filed Sept. 27, 1940 3 Sheets-Sheet 2 INVENTORHERBERT M WAGNER Zur TTORNE Y Aug- 13, 1942- H. M. WAGNER 2,293,418

ELECTRON DI SCHARGE DEVICE Filed Sept. 27, 1940 l I5 Sheets-Sheet 3INVENTOR HERBERT M. WAGNER A TTOHNE Y Patented Aug. 18, 1942 ELECTRONDISCHARGE DEVICE Herbert M. Wagner, Newark, N. J.,

asslgnor to Radio Corporation of America, a corporation of DelawareApplication september 27, 1940, serial No. 358,629

20 Claims.

My invention relates to electron discharge devices, more particularly tobeam tubes utilizing an orbital beam and secondary emissionamplification and useful for many different applications at both low andultra high frequencies.

Straight beams and secondary emitting surfaces have been utilized forincreasing the transconductance of conventional and beam type tubesbutwhere the straight beam is used and where secondary emitting surfacesare exposed directly to the cathode, material evaporated from thethermionic cathode may deposit on the secondary emitting surfaces andcause reduction of emission from the secondary emitting surfaces.Further, where straight beams are used comparatively long beam paths arenecessary to provide a desirable sensitivity where deflection is usefuland in some tubes of this type the Ibeam focus is affected when the beamis dee'cted by the defiecting electrodes, especially when a singledeflection electrode is used for control instead of a push-pullarrangement of deilecting electrodes. In order to accommodate theelectrode system of straight beam tubes, the tube envelopes must be ofsome length and sometimes of an odd shape.

In utilizing conventional radio tubes at the ultra-high frequencies asamplifiers, one of the diiculties encountered is excessive couplingbetween the input and output electrodes. To overcome this difficulty aseparation of function between the control electrodes and outputelectrodes must be .provided for. Excessive coupling is usually due tomutual capacitance and mutual inductance between electrodes, the leadsand other circuit elements. While very thorough shielding, the use ofshort leads and the use of novel circuits serve to rectify thisdifficulty at least to a certain extent, in many cases, to reduce theinterelectrode coupling, a considerable increase in separation betweenthe high frequency electrodes must be made, which in turn affects theoperation of the tube at high frequencies when the transit time of theelectrons becomes important. Again at the high frequencies in beam typetubes utilizing orbital beams, due to the transit time of the electronsat high frequencies and particularly where secondary electrons areutilized, the electrons may be collected at the output electrode in -anout of phase relation,- reducing the effectiveness of the device.

In automatic andA manual volume control circuits where 'customary gridbias control .is used, due tothe fact that the cathode current does notremain constant, achange in input capacihigh frequency circuits results.Hence, means which will permit control of the volume without changingthe cathoder current is desirable.

It is therefore the principal object of my invention to provide anelectron discharge device employing a lbeam and secondary emissionamplification, and having improved characteristics.

More specifically an object of my invention is to provide such anelectron discharge device in which the secondary emitting surfaces areprotected from deposition of evaporated material from the -cathode whichwould reduce the secondary emitting qualities of the secondary emittingsurfaces.

Another object of my invention is to provide an electron dischargedevice utilizing a beam and having an increased sensitivity overconventional beam devices using straight beams and of comparable overalldimensions.

Another object of my invention is to provide an electron dischargedevice in which both the input and output capacitances are reduced.

A further object of my invention is to provide a beam tube in whichWhile the sensitivity is increased no ill elects of defocusing of thebeam are experienced when the deflecting electrodes go into operation.

It is a still further object of my invention to provide such a deviceparticularly suitable for use at high frequencies and in which theundesirable effects of the transit time of the electrons in said deviceswhen utilized at high frequencies are substantially eliminated.

Another object of my invention is to provide an electron dischargedevice which is particularly suitable as an amplifier at ultra highfrequencies.

Still another object of my invention is to provide an electron dischargedevice employing a beam which is particularly suitable for volumecontrol purposes at high frequencies.

The novel features which I believe to be characteristic of my inventionare set forth with `particularity in the appended claims, but theinvention itself will best be understood by reference to the followingdescriptionl taken in connection with the accompanying drawing in whichFigure 1 is a transverse view of an electron discharge tance andAdamping and consequent detuning in device made according to myinvention and its associated circuit when utilized as an automaticvolume control device, and Figure 2 is a top end view of the electrodemount partially schematic for clarity of a modification of the electrondischarge device shown in Figure 1, and its associated circuit when usedas a mixer tube, Figure 3 is a longitudinal section of the tube shown inFigure 2, showing details of construction, and F1B ure 4 shows the leadarrangement and detalls of construction of the. tube shown in Figure 3.

Referring to Figure 1, an electron discharge device made according t myinvention comprises an evacuated envelope I0 containing the electrodesof the electron discharge device. A flat cathode II coated on oppositesides with. emitting material is surrounded by a control grid I2, andprovides a pair of oppositely disposed beams from the cathode. Beamforming electrodes I3 normally maintained at cathode potential arepositioned outside the control grid and between the control grid I2 andscreen grid. I4. The oppositely directed beams indicated by the dottedlines pass between the oppositely disposed surfaces of the tubularelectrode I and inner tubular electrode I6 provided with an open-` ingI1 substantially 180 removed from the cathode and having radialshielding extensions` I8. A secondary emitting electrode I9 is disposedoutside of and opposite opening `II in the inner tubular member I6. Itis'provided with an extending V-shaped surface 20 for purposes to bedescribed below. 'I'he surface of electrode I9 facing the opening iscoated with material. for emitting secondary electrons when struck by'the electron beams from the cathode II. Positioned within the openingI'I and oppositelydisposed to the V-shaped surface of the secondaryemitting electrode I9 is the nat output electrode 2I.

An input circuit 22 is connected between the control grid I2 and thecathode, and the output circuit 24 to the output electrode 2|. 'I'heautomatic volume control voltage may be applied tcl the outer tubularmember I5 at the terminals 23. A source of voltage for applying properpo-l tentials to the various electrodes is indicated at 25.

In operation the beam is directed against the inclined surfaces of theV-shaped portion 2li of the output electrode for releasing secondarieswhich travel toward andare collected by the output electrode 2|. If thedevice is used as a mixer tube the local oscillating frequency may beapplied to the electrode I5, causing the beam to travel between the twopositions indicated by the dotted lines 6 and 9, the input voltage beingapplied to the control grid. When used as an automatic volume controltube the outer elec-1 trode I5 may again be used to deflect the beam sothat more or less of the beam strikes the emitting surface of electrodeI9 to vary the output current. The advantages of using the tube as avolume control device is that the current and transconductance of theoutput electrode can be controlled by deiiecting the electron beamwithout varying the cathode Current which remains substantiallyconstant. This aVOdS Changes in input capacitance and the consequentdetuning which would result in high frequency circuits.

Electrode I9 is specially formed so that the Spacing between it andelectrode 2I decreases toward the center of the electrodes, that is to-Ward the apex of the V. Electrons from different parts of lthe cathodeleaving the cathode at the same time may strike different portions O fthe V-Shaped part 20 of the secondary emitting electrode I9. Thosehitting nearer the edges of the electrode 20 reach that electrode soonerbecause they have a shorter orbital path to bers 35.

travel than electrons hitting nearer the apex of the V. Thus secondaryelectrons are released sooner nearer the outer edges of the electrode I9than nearer the apex of the V-shaped surface by primary electronsleaving the cathode the same time. But the secondary electrons from thesurface of electrode I9 nearer the outer edge of the electrode requiremore time to reachelectrode 2| than the secondary electrons releasedfrom the apex of the V-shaped portion of the secondary emitting surfacesince they have a greater distance to travel. Hence substantially all ofthe secondary electrons released by the primary electrons leaving thecathode together reach the surface of electrode 2I and are absorbed bythis electrode at substantially the same time and in the proper phaserelationship. This difference in the time of travel or transit time ofthe primary and secondary electrons becomes important at the ultra highfrequencies. The shaping of the electrodes provides not only properspacing but a desirable` electrostatic iield and also preventsinteraction between the two oppositely directed beams. While shown as aV, other arrangements will satisfy the requirements for proper operationat high frequencies provided thatthe surfaces of the secondary electronemitting electrode and the output electrode approach each other intravelling toward the center of the electrodes. AThus the V-shapedportion could, for example, be replaced by a rounded portion and theplane surface of the collector by some other surface whereby the spacingbetween the electrodes increases as the outer edges of the electrodesare approached.

The modication shown in Figure 2 comprises envelope SUcontainng the natcathode 3|, control grid 32 and screen grid 33. A tubular electrode 34is positioned with respect to the cathode so that oppositely directedbeams pass along the inner surface of this electrode. The inner tubularelectrode in this case comprises a pair of arcuate shaped members 35electrically connected to the shield member 36. The beams are directedbetween the oppositely disposed surfaces of the outer tubular electrode34 and the arcuate shaped electrodes 35. The secondary emittingelectrode 3T is disposed 180 removed from the cathode and is providedwith a rounded raised surface which could be of V-shape extending towardthe output electrode 38 positioned within the opening formed by thearcuate shaped mem- This modification is shown used in connection with amixer tube circuit, the input being applied to the control grid 32 byinput circuit 39 and the local oscillator voltage to the electrode 34 bythe oscillator circuit, the output circuit 4I being connected to theoutput electrode 38, the source of voltage 42 providing the voltages forthe various electrodes.

One very effective means of minimizing input capacitance in a receivingtube is to use small input electrodes, for example, a small cathode andcontrol grid which provide a small modulated current, and then makinguse of the phenomena of secondary emission to generate a vlargercurrent, thus effectively increasing the transconductance of the lowcapacitance input structure.

The actual constructional features of a tube for accomplishing thispurpose and incorporating the electrodes shown in Figure 2 are shown inFigures 3 and 4. As there shown the cathode 3|, which is made nat inorder to produce two we defined beams, emerging from the cathode inopposite directions, control grid 32 and screen grid 33 are supportedbetween a pair of insulating supports and spacers and 46 which may be ofmica. all of these electrodes being shorter than the other electrodescomprising themount. This assembly is supported by and locked to theshield 36 by extending the micas .45 and 46 through slots in the shield36 and extending a locking rod 41 through apertures in the mica andwelding or otherwise securing this side rod or locking rod to theshield.

One of the reasons for making the cathode, control grid and screen gridassembly shorter in length than the rest of the electrodes was toeliminate the eifects of theelds at the top and bottom of the mount. Itis desirable tosubject the electrons to substantially the same iieldthroughout the 'beam and by keeping the electron beam away from theupper and lower ends of the mount the electrons are subjected to a moreuniform field than they would otherwise be. While it would have beenpossible to reduce the emitting surface by spraying only a portion ofthe cathode and extending the cathode and grid wires through the top andbottom micas 48 and 49, this would increase the interelectrodecapacities and make the cathode and grid assembly less rigid forassembly.

In order to obtain maximum current controlling action by the controlgrid 32,.it is mounted as close as practical to the cathode. Thesubsequent current multiplication at the secondary emitter increases theeifectiveness of grid control by a factor approximately equal to thesecondary emission ratio which in tubes made according to the presentinvention is about five. Thus a small control grid having a lowinterelectrode capacitance eiectively controls a large output current,which is an important factor for Wide-band operation. From the highfrequency standpoint this feature is also beneficial because lowcapacitance produces low circulating current and thus circuit losses arereduced.

A pair of mica spacers 48 and 49 have positioned between them andsupport the outer cylindrical electrode 34 secured to the mica by meansof extensions 50 and 5| extending through the micas. The arcuate shapedelectrodes 35 are secured to the mica by means of ears or extensions 52and 53 extending through the micas, the extension 52 being bent overagainst the mica and the ear 53 secured to a shield 54 which is alsoelectrically connected to the rod 41 and shield 36 so that the topshield 54 and shield 55 at the bottom of the mount are electricallyconnected. The lower end of shield 35 is also electrically connected tothe lower shield 55 by extensions 53' of members 35. These two shieldseffectively shield the output comprising the secondary emitter 31 andoutput electrode 38. from the input. Getter assemblies 56 and 51 may beprovided at the top and bottom of the mount.

As shown in Figure 2, the focusing system consisting of the outertubular member 34 and inner arcuate-shaped members 35 provide a radialfield between them which deflects the electrOn beams toward thesecondary emitter 31. The radial field in addition to deecting beamstends to focus the electrons. The two beams which initially leave thecathode are slightly diverging when issuing from the openings of thescreen grid 33 but are focused by the action of the radial eld toconverge on the emitter electrode 31.. 'I'hus the width of the beam onthe secondary 75 emitter may be reduced to the width of the primarycathode. For best focusing action the potentials on the focusingelectrodes and the velocity of the electrons in the beam must beproperly adjusted. The electrodes in the tube are designed so that goodfocusing is obtained when the voltage on the outer cylinder or tubularmember 34 is made zero or slightly negative with respect to the cathode,when the tube is used as an amplifier.

ABecause the secondary emitter 31 and output electrode 38 are mounted onthe side of the tube opposite the cathode side, the focusing electrodes35 and shield 36 serve as a screen between the input and output of thetube; that is, between the cathode and vthe secondary emitter and outputelectrode, so that material evaporated from the oxide coated cathode,which would affect the secondary emitting surfaces, impinges on thetubular electrodes rather than on the secondary emitting surface.

The loss of transconductance due to space charge effects during electrontransit time from the screen 33 to the secondary emitter is small eventhough the transit time from the screen to the emitter may be comparableto the period of oscillation. This result is due to the fact thatcurrent inthe long beam is comparatively small. The effect is, that thelarge output current is generated only at the secondary emitter, and thetransit time of secondary electrons to the plate is short.

As shown in Figures 3 and 4, the mount assembly is electricallyconnected to and supported by radially extending leads which are sealedinto the radial lip 59 formed when the upper and lower cup-shapedportions of the tube envelope are sealed together. The lead arrangementis best shown in Figure 4 which also shows details ofv construction ofthe lower end of the tube. Two leads are provided for most of theelectrodes with the low potential leads positioned to act as shields forother electrode leads. As shown the two control grid leads 32 areshielded by means of the low potential cathode leads 3l 1, the cathodeheater leads 3l being positioned on the other side of the cathode leads.The outer tubular lead 34vand the screen lead 33' are electricallyshielded by means of the shield leads 35 connected to shield 35, theshield 55 and leads 35' shielding the secondary emitter lead 31' andoutput electrode lead 38. Thus in the arrangement shown maximumshielding and separation are provided between input and outputelectrodes and electrode leads. The use of two leads for the sameelectrode minimizes lead inductance and reduces loss due to circulatingcurrents. The two cathode leads provide low impedance for thegrid-cathode circulating current. All of the auxiliary electrodes may beby-passed to radio frequency ground by means of by-pass condensers andcircuits connected to the tube. At the highest frequencies specialcircuits may be used to tune out lead impedance.

Tubes made according to my invention have trans-conductances ofapproximately 20,000 micromhos while some tubes tested as high as 24,000rnicromhos.v Tubes incorporating my invention have also shown a gain of6 and '7 when used as wide-band ampliers at 400 or 500 megacycleoperation.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it will be apparentthat my invention is by no means limited to the exact forms illustratedor the use indicated, but that many variations may be made in theparticular structure used and the purpose for which it is employedwithout departing from the scope of my invention as set forth in theappended claims.

What I claim as new is:

1. An electron discharge device including an envelope containing acathode for supplying electrons, a control grid for said cathode andmeans for forming electrons from the cathode into a beam, meansincluding a second control electrode adjacent the beam of electrons forcausing said beam to travel along a curved path, an electrode positionedin the path of said beam and coated with emitting material for emittingsecondary electrons when struck by said beam, and an output electrodeadjacent the secondary electron emitting electrode for receivingsecondary electrons emitted by said secondary electron emittingelectrode, said output electrode being positioned between the cathodeand the secondary emitting electrode and having a plane surface and thesecondary emitting electrode having a plane surface disposed at an angleto said output electrode, and means for shielding said output electrodefrom direct bombardment by the electron beam.

2. An electron 'discharge device including an evacuated envelopecontaining a cathode for supplying electrons, and means for formingelectrons from the cathode into a. beam, a control electrode for saidbeam of electrons, an electrode positioned in the path of the beam andcoated with emitting material' for emitting secondary electrons whenstruck by said beam, and an output electrode adjacent the secondaryelectron emitting electrode and between said cathode and secondaryemitting electrode for receiving secondary electrons emitted by saidsecondary electron emitting electrode, said secondary emitting electrodeand said output electrode having surfaces approaching each other in thedirection of travel of the electron beam, and means for shielding saidoutput electrode from direct bombardment by the electron beam.

3. An electron discharge device having an envelope containing a cathodefor emitting electrons, a grid surrounding the cathode, means adjacentthe grid and cathode for forming electrons from the cathode into a pairof oppositely disposed beams, means in the path of said beams forcausing said beams to travel curved paths and including a second controlelectrode, an intercepting electrode for intercepting the beams andcoated with secondary emitting material for releasing secondaryelectrons when struck by said beams,said intercepting electrode having aV-shaped surface and an output electrode having a plane surfaceoppositely disposed to said V-shaped surface, the surfaces of theV-shape being directed at an angle to the plane surface of the outputelectrode, the peak .of said V-shaped surface being closest to saidplane surface of the output electrode, and means for shielding saidoutput electrode from direct bombardment by the electron beam.

4. An electron discharge device including an evacuated envelopecontaining a cathode for supplying electrons, and means for formingelectrons from the cathode into a beam, a control electrode for saidbeam of electrons, means in- 'ATO cluding a second control electrodeadjacent the beam of electrons for deflecting said beam, an electrodepositioned in the path of the beam and coated with emitting material foremitting secondary electrons when struck by said beam, and an outputelectrode adjacent the secondary electron emitting electrode and betweensaid cathode and output electrode for receiving secondary electronsemitted by said secondary electron emitting electrode, said secondaryemitting electrode and said voutput electrode having surfacesapproaching each other in the direction of travel of the electron beam,and means for shielding said output electrode from direct bombardment bythe electron beam.

5. An electron discharge device having an envelope including a cathodesurrounded by a control grid, means for forming the electrons from thecathode into a beam, a pair of concentric tubular electrodes, one ofsaid tubular electrodes being positioned on each side o'f said cathodeand control grid so that the beam of electrons passes between theopposed surfaces of the tubular electrodes for causing said beam totravel a curved path, the inner tubular electrode being provided with anopening removed substantially from the cathode, and an electrodepositioned in the path of the beam and having a plane surface, saidsurface being coated with secondary electron emitting material wherebysecondary electrons are released from said surface when struck by thebeam of electrons, and an output electrode positioned in the opening inthe inner tubular electrode and having a. plane surface positioned at anangle to the surface coated with secondary emitting material forcollecting secondary electrons.

6. An electron discharge device having an evacuated envelope containinga cathode for emitting electrons, a. grid surrounding the cathode, meansfor forming said electrons into a pair of oppositely disposed beams,means in the path of said beams for causingV said beams to travel curvedpaths and including a second control electrode, an electrode forintercepting the beams and coated with secondary electron emittingmaterial for releasing secondary electrons when struck by said beams, anoutput electrode adjacent the secondary electron emitting electrode andbetween said cathode and the secondary emitting electrode for receivingthe secondary electrons, said intercepting electrode and said outputelectrode having surfaces approaching each other in the direction oftravel of the electron beams, and means for shielding said outputelectrode from direct bombardment by the electron beam.

7. An electron discharge device having a cathode surrounded by a controlgrid and means for forming electrons from the cathode into a pair ofoppositely disposed beams, a pair of concentric tubular electrodesmounted adjacent the cathode and the control grid so that the beams ofelectrons pass between the opposed surfaces of the tubular electrodesfor causing said beams to travel curved paths, the inner tubularelectrode having a longitudinal opening on the opposite side of thetubular electrode from the cathode, an output electrode positionedwithin said opening and having a plane surface, an electrode positionedbetween the outer tubular electrode and the output electrode forintercepting the electron beams and having a V-shaped surface extendingtoward said opening and said output electrode whereby secondaryelectrons released from the surfaces of the V-shaped portion of thesecondary emitting electrode are absorbed by the output electrode.

8. An electron discharge device having an envelope containing a cathodefor emitting electrons, a grid surrounding the cathode, means adjacentthe grid and cathode for forming electrons from the cathode into a pairof oppositely disposed beams, means in the path of said beams forcausing said beams to travel curved paths toward each other andincluding a second control electrode, an electrode for intercepting saidbeams and coated with secondary emitting material for releasingsecondary electrons when struck by said beams, said interceptingelectrode having a raised surface intermediate its ends for interceptingsaid beams and keeping said beams separated, and an output electrodehaving a. plane surface oppositely disposed to said raised surface, theraised surface of the secondary emitting electrode and the plane surfaceof the output electrode approaching each other in the direction oftravel of the electron beams toward the center of said raised surface,and means for shielding said output electrode from direct bombardment bythe electron beam. c

9. An electron discharge device having an envelope including a cathodefor supplying electrons, means for forming electrons from the cathodeinto a beam, a pair of concentric tubular electrodes, one of saidconcentric electrodes, being positioned on each side of the cathode sothat the beam of electrons passes between the opposed surfaces of theconcentric electrodes causing said beam to travel a curved path, theinner concentric electrode being provided with an opening removedsubstantially 180 from the cathode and an electrode positioned in thepath of the beam opposite said opening and coated with secondaryelectron emitting material whereby said secondary electrons are releasedfrom said surface when struck by said beam of electrons, an outputelectrode positioned in the opening in the inner concentric electrodeand having a plane-surface positioned at an angle to the lsurface coatedwith secondary emitting material for collecting secyondary electrons.

1.0. A11 electron discharge device having an envelope including acathode for supplying electrons, means for forming electrons from thecathode into a beam,'a pair of concentric tubular electrodes, one ofsaid concentric electrodes being positioned on each side of the cathodeso that the beam'of electrons passes between the opposed surfaces of theconcentric electrodes causing said beam to travel a curved path, theinner concentric electrode being provided with an opening removedsubstantially 180 from the cathode and an electrode positioned in thepath of the beam opposite said opening, and an electrode positioned inthe opening in the inner concentric electrode.

11. An electron discharge device having a cathode surrounded by acontrol grid and means for forming electrons from the cathode into apair of oppositely disposed beams, a pair of concentric tubular membersmounted adjacent the cathode and the control grid so that thebeams ofelectrons pass between the opposed surfaces Y of the tubular electrodesfor causing said beams to travel curved paths, the inner tubular mem-Aber having a longitudinal opening on the opposite side ofthe tubularmember from the cathodev and radial ns extending outwardly from thelongitudinal edges of'said opening, an out- 75 put electrode positionedwithin said opening and having a plane surface, an electrode positionedbetween the outer tubular electrode and the output electrode forintercepting the electron beams and having a v-shaped surface extendingtoward said opening and said output electrodewhereby secondary electronsreleased from the surfaces of the V-shaped portion of the secondaryemittting electrode are absorbed by the output elecrode.

12. An electron discharge device having a cathode surrounded by acontrol grid and a screen grid, and electrodes between said grids forforming electrons from the cathode into a pair of oppositely disposedbeams, a pair of concentric tubular members mounted adjacent the cathodeand the control grid so that the beams of electrons pass between theopposed surfaces of the tubular electrodes for causing said beams totravel curved paths, the inner tubular member having a longitudinalopening on the Yopposite side of the tubular member from the cathode, anoutput electrode positioned within said opening and having a planesurface, an electrode positioned between the outer tubular electrode andthe output electrode for intercepting the electron beams and having aV-shaped surface extending toward said opening and said output electrodewhereby secondary electrons released from the surfaces of the V-shapedportion of the secondary emitting electrode are absorbed by the outputelectrode.

13. An electron discharge device having an envelope including a cathodesurrounded by a control grid and means for forming electrons from thecathode into a pair of oppositely disposed beams, a, tubular electrode Ysurrounding said cathode and control grid but eccentric thereto, aninner electrode comprising a pair QI oppositely disposed arcuate shapedmembers adjacent the cathode and control grid and within said tubularelectrode, the oppositely disposed electron beams from the cathode beingdirected between the opposed surfaces of the tubular electrode and thearcuate shaped elements of the inner electrode during operation of theelectron discharge device, a secondary emitting electrode positionedwithin said tubular electrode and on the opposite side of the innerelectrode from said cathode and an output electrode positioned oppositethe secondary emitting electrode and within the space provided betweenthe arcuate shaped members of the inner electrode for receivingsecondary electrons from the secondary emitting electrode.

14. An electron discharge device having an envelope including a cathodesurrounded by a control grid and means for forming electrons from thecathode into a pair of oppositely disposed beams, a tubular electrodesurrounding said cathode and control grid but eccentric thereto, aninner electrode comprising a pair of oppositely disposed arcuate shapedmembers adjacent the cathode and control grid vand within said tubularelectrode, the oppositely disposed electron beams from the cathode beingdirected .between the opposed surfaces of the tubular electrode and thearcuate shaped elements of the inner electrode during operation of theelectron discharge device, a secondary emitting electrode positionedwithin said tubular electrode and on the opposite side ofthe innerelectrode from said cathode, and an output electrode positioned betweenlthe secondary emitting electrode and within the space provided betweenthe arcuate shaped members of the inner electrode for receivingsecondary electrons from the secondary emitting electrode, saidsecondary emitting electrode having a V-shaped surface extending towardthe output electrode and said output electrode having a plane surfacetransverse to the apex of the V-shaped surface.

An electron discharge device having an envelope containing an electrodeassembly comprising a. cathode surrounded by a control grid and screengrid, and including means for forming the electrons emitted by thecathode into two oppositely directed electron beams, a tubular electrodeprovided with a longitudinal slot and substantially surrounding thecathode, control grid and screen grid but eccentrically positioned withrespect thereto whereby a portion of the electrode assembly extendsthrough said longitudinal slot, an inner electrode centrally disposedwith respect to the tubular electrode and having a pair of oppositelydisposed arcuate shaped elements electrically connected together, thebeam from the cathode being directed between the oppositely disposedsurfaces of the outer tubular electrode and the inner electrode duringoperation of said electron discharge device, a secondary emittingelectrode positioned within the outer tubular electrode and on theopposite y side of the inner electrode from said cathode and providedwith a surface coated with secondary electron emitting material forintercepting the electron beams and an electrode having a plane surfacepositioned within the arcuate shaped members and oppositely disposed tosaid surface of the secondary emitting electrode to receive secondaryelectrons from the said surface.

^ 16. An electron discharge device including an evacuated envelopecontaining a cathode surrounded by a control grid, said cathode andcontrol grid being supported between a pair of spaced insulatingmembers, a tubular electrode surrounding said cathode and grid andeccentric therewith, an electrode oppositely disposed to said cathodeand grid Within said tubular electrode, and an electrode comprisingarcuate shaped elements and a sheet metal shielding member positionedbetween the cathode and the electrode oppositely positioned thereto, theinsulating members supporting said cathode and grid extending throughand supported by said shielding member, and insulating supportingmembers secured to said tubular electrode insulatingly supporting theother electrodes and shielding member within the tubular electrode.

17. An electron discharge device comprising an evacuated envelope andcontaining a cathode, control grid and screen grid, and a pair ofsupporting and spacing insulating members secured to opposite ends ofthe cathode and grids, a tubular electrode eccentric with respect to andsurrounding said cathode and grids, and a pair of oppositely disposedelectrodes positioned within but on the opposite side of the tubularelectrode from the cathode and grids, an electrode intermediate saidcathode and pair of oppositely disposed electrodes and comprising asheet metal shielding electrode and a pair of oppositely. disposedarcuate shaped elements providing with the tubular electrode a curvedpassageway between the cathode and the oppositely disposed electrodes,the insulating members supporting the cathode and grids extendingthrough and supported by the shielding electrode, and sheet insulatingmembers at the opposite ends of the tubular electrode supporting theother electrodes within the tubular electrode, the cathode and gridsbeing of shorter length than said tubular electrode.

18. An electron discharge device comprising an evacuated envelope andcontaining a cathode, control grid and screen grid, and a pair ofsupporting and spacing insulating members secured to opposite ends ofthe cathode and grids, a tubular electrode eccentric with respect to andsurrounding said cathode and grids, and a pair of oppositely disposedelectrodes positioned within but on the opposite side of the tubularelectrode from the cathode and grids, an electrode intermediate saidcathode and pair of oppositely disposed electrodes, and comprising asheet metal shielding electrode and a pair of oppositely disposedarcuate shaped elements providing with the tubular electrode a curvedpassageway between the cathode and the oppositely disposed electrodes,the insulating members supporting the cathode and grids extendingthrough and supported by the shielding electrode, and sheet insulatingmembers at the opposite ends of the tubular electrode supporting andspacing the other electrodes within the tubular electrode, the cathodeand, grids being of shorter length than said tubular electrode, and ishielding members extending above and below the sheet insulating membersfor shielding the oppositely disposed electrodes from the otherelectrodes within the envelope.

19. An electron discharge device comprising an evacuated envelope andcontaining a cathode, control grid and screen grid, and a pair ofsupporting and spacing insulating members secured at opposite ends ofthe cathode and grids, a tubular electrode eccentric with respect to andsurrounding said cathode and grids, and a pair of oppositely disposedelectrodes positioned within :but on the opposite side of the tubularelectrode from the cathodeA and grids, an electrode intermediate saidcathode and pair of oppositely disposed electrodes and comprising asheet metal shielding electrode and a pair of oppositely disposedarcuate shaped elements providing with the tubular electrode a curvedDas-l sageway between the cathode and the oppositely disposedelectrodes, the insulating mem-bers supporting the cathode and gridsextending through and secured to the shielding electrode, and sheetinsulating members at the opposite ends of the tubular electrodesupporting 4and spacing the other electrodes within the tubularelectrode, and shielding members extending above and below the sheetinsulating members for shielding the oppositely disposed electrodes fromthe other electrodes Within the envelope, and radial leads extendingthrough the wall of the envelope and electrically connected to thevarious electrodes within the envelope.

20. An electron discharge device including an evacuated envelopecontaining a cathode and a closely spaced control grid and screen gridsurrounding said cathode, and a pair of insulating spacer members atopposite ends of the cathode and grids supporting said cathode and gridsin spaced relation, a tubular electrode lying along thessamelongitudinal axis as said cathode and surrounding said cathode and gridsbut eccentric thereto, a secondary 'emitting electrode and an oppositelydisposed output electrode positioned at the other side but within saidtubular electrode, an electrode intermediate the cathode and thesecondary emitting and output electrodes and comprising a sheet metalshield member transverse to the plane passing through the cathode andoutput electrode, and apair of arcuate shaped members at opposite sidesof the metal shield and forming with the outer tubular electrode curvedpassageways between the cathode and the secondary emitting electrode,the insulating spacer members supporting the cathode and grids extendingthrough said shield member and secured thereto supporting the cathodeand grids in a spaced relation with respect to said tubular member, saidoutput electrode lying between the arcuate shaped members on one side ofthe shield member and the cathode and grid assembly extending betweenthe arcuate shaped members on the other side of the shield member, theelectrons from the cathode passing between the surfaces of the arcuateshaped members and the outer tubular electrode during operation of saidelectron dis- HERBERT M. WAGNER.

10 charge device.

